In order to clamp parts of machines to each other, accurately and safely, use is generally made of screws, bolts and other similar means. Where the connected parts are subjected to high stresses and must frequently be disassembled and reassembled it is clear that the number of screws that must be handled are far too much time and the work becomes incompatible with economic and competitive production. FIG. 1, for example, shows a system at present used in the presses for making ceramic tiles to connect the upper and lower dies each other.
It will be seen from the figure that situated between the upper plate (10), heated by elements (11) and the block (12) heated by elements (13), there are the lower die (14) and the upper die (15) which, when pressure is applied, press on the tile (16) retained at its perimeter by a matrix die (17).
The upper die (15) is held to the upper plate (10) by a series of cheese-headed screws (18) and the lower die (14) is also fixed by cheese-headed screws (20), but between the head of the screw (20) and the die (14) there are two Belleville washers (25-26).
Due to a high pressure applied and to heating, the humidity contained in the clay of which the tile is made, evaporates leaving deposits of lime on the sides of each die, which leads to heavy wear and makes it necessary to replace the pads frequently.
There are many of these dies to be periodically replaced in each press and numerous screws holding them in position consequently should be often replaced, with the press out of action, the time required for replacement is long, making for higher costs of production and lower output.
If quicker means are employed, such as levers, clamps and the like, though this may make it quicker and simpler to disassemble and reassemble the opposed parts, there is generally an adverse effect on safety and accuracy.